1. Field of the Invention
The present invention relates to a back light unit, and more particularly, to a back light unit for a display apparatus.
2. Discussion of the Related Art
A liquid crystal display (hereinafter, shortly referred to as “LCD”) apparatus is configured to adjust a brightness and darkness by changing the arrangement of liquid crystals introduced into a liquid crystal panel, and to display an image as light beams penetrate the adjusted bright and dark regions.
However, since the liquid crystal panel has no self-illumination function, the LCD includes a back light unit (BLU) to provide a rear surface of the liquid crystal panel with light beams.
The BLU includes a light source, a light guide panel, a reflector sheet, first and second diffuser sheets, and first and second prism sheets.
The light source is a device to generate light beams. A light emitting diode (LED), a cold cathode fluorescence lamp (CCFL), and a laser light source are mainly used as the light source.
The light guide panel uniformly transmits the light beams, generated from the light source, up to an upper surface thereof.
The reflector sheet reflects light beams, which proceeded to a lower surface and a side surface of the light guide panel, to the upper surface of the light guide panel.
The first diffuser sheet diffuses the light beams having passed through the light guide panel.
The first and second prism sheets adjust the proceeding direction of the light beams diffused from the first diffuser sheet.
The second diffuser sheet diffuses the light beams having passed through the first and second prism sheets, to introduce the light beams into the liquid crystal panel.
In the above described back light unit, however, there is a problem in that, when a LED or CCFL is used as the light source, the resulting BLU has an increased volume or deteriorated color reproducibility.
Further, when a laser light source is used as the light source, although the BLU has a superior system organization efficiency or color reproducibility, it is difficult to achieve uniform illumination due to a small radiation angle.